The present invention relates to a forward turret of a drilling apparatus or so-called "roof bolter", particularly for use in drilling a hole in the roof of a mine, and enabling the injection of resin cartridges or the like in the hole to secure one end of a bolt in the hole and enabling the other end to support the roof of a mine gallery.
Former support techniques include the use of expansion bolts having expandable anchor members at one end thereof. With the bolt inserted in the hole, the bolt is rotated to secure the bolt in the base of the hole by means of expansion, and after which further tightening of this bolt causes the compression of the ground in the form of a column coaxial to the said bolt. To carry out the drilling of the hole, the positioning of the bolt and the tightening of the bolt, it is known to use an apparatus comprising a pivoting turret supporting a drilling carriage and a bolting carriage. The first of these carriages is a drilling machine which enables the initial drilling of the hole, after which the turret is rotated about its pivot axis such that the second carriage is brought into the axis of the previously drilled hole for the insertion and tightening of the bolt. Apparatus of this type is disclosed in particular in U.S. Pat. No. 3,246,705.
Developments in support techniques led to the replacement of the expansion bolts by resin-sealed bolts. The resin used takes the form of elongate cartridges. These may be inserted manually into the previously drilled hole, before the positioning of the bolt. However, the manual insertion of the cartridges requires time and skilled operators. In addition, it is difficult to carry out if the roof of the mine is particularly high. It has therefore been attempted to reduce the manual work required for this operation by adding a resin cartridge injection device to the drilling and bolting turrets. After the hole has been drilled, the turret is pivoted into an intermediate position in which the cartridge injection device is located in the axis of the bolt. One or more cartridges are then inserted into the hole by mechanical or pneumatic means. Finally, a further pivoting of the turret brings the bolting carriage into the axis of the hole into which the resin cartridges have been inserted. A "three-position" turret of this type is disclosed, for example in the Published German Pat. No. 2 222 646. However, with the turret of "three-position" type, there is always a risk, despite the fact that the turret is anchored in the roof along its pivoting axis, that after the first rotation of the turret the cartridge injection device may not be brought exactly into the axis of the hole drilled in the initial position of the turret. In order to avoid this problem, it has already been envisaged to provide a turret in which the drilling of the hole and the injection of the cartridges are carried out successively without moving the turret. For this purpose, the forward head of the turret is provided with a first passage for the drilling rod and a second passage for the admission of the resin cartridges, this second passage intersecting and opening into the first passage at an angle of approximately 30.degree. see U.S. Pat. No. 4,398,850. After drilling of a hole, the drilling rod is therefore retracted and, without displacing the turret which remains anchored to the rock, the resin cartridge(s) are injected into the hole via the second passage and then the first passage of the turret head. A single rotation of the turret is then sufficient to bring it into a second position enabling bolting. This enables the structure of the turret to be simplified as compared to the "three-position" turret.
However, in the case of the two-passage turret head each cartridge of resin must pass, during its travel, through a bend which is fairly pronounced and which corresponds to the connection between the two passages provided in the forward head of the turret. This leads to various drawbacks including the following:
Deflection of the cartridge with respect to the theoretical axis of injection during passage through the bend, this phenomenon being amplified by wear of the outer end of the first passage in the forward head with the result that the deflected cartridge tends to catch on the inlet of the drilled hole.
Friction of the cartridge against the walls of the forward head passages, this friction required the use of reinforced cartridges and causing a loss of kinetic energy preventing full penetration of the cartridge into the drilled hole (i.e., to the base of the hole). This drawback is particularly great when several cartridges are to be injected into the same hole.
As the cartridge injection passage communicates with the drilling rod passage, the flexible injection hose which delivered the resin cartridge to the cartridge injection passage is not sheltered from rock debris and water resulting from the drilling operation. It is then necessary to blow compressed air through this hose during and/or after drilling, which leads to a loss of time and causes the operator and the apparatus to be sprayed with water and debris.
The forward turret head having its two passages connected in the form of an elbow joint, is of comparatively large size, in particular in the longitudinal direction of the turret which limits the travel of the drilling machine.
The forward turret head must be completely replaced if it is desired to drill holes and inject cartridges having different diameters.